Incompatible change Commands in the
CryptoAPI and Certificates modules that have an -encoding option have changed behaviour. For input, if
-encoding is not specified, they now try to
determine the input encoding instead of defaulting to DER. For
output, the default encoding has changed from DER to PEM.

Incompatible change The crypt_acquire
command behaviour has changed. It now takes the key container name
as the -keycontainer option instead of the first
argument. The -create option will not raise an
error if the key container already exists. The option -verifycontext now defaults to a value that is dependent
on other arguments.

Major changes in this release are support for Windows event
tracing, new Windows event logging API, SSL/TLS sockets, greatly
enhanced support for CryptoAPI including certificate handling,
access to performance counters, enhancements to the COM module and
architectural changes for modularity and run-time performance.

Make a special note of the list of Incompatible
Changes at the end of this section. Some of these
differences apply to prior 4.0 betas as well.

Added COM support for passing SAFEARRAY types as input
parameters and enhanced output SAFEARRAY values to support
multidimensional arrays. POTENTIAL
INCOMPATIBILITY as previously multidimensional arrays were
returned as a single list.

Performance related options have been removed.
Equivalent functionality is available through pdh_system_performance_query. The command now returns
information about the current processor group, not the whole
system.

Many commands which take a password as an argument
now expect it to be passed in encrypted form as returned by
read_credentials, credentials_dialog and conceal. Unencrypted
forms of passwords are still accepted by existing commands but are
deprecated and support will be dropped in a future release.
Commands new in 4.0 will only work with the new encrypted password
forms.

INCOMPATIBILITY This version supports
Windows XP or later versions of Windows and version 8.5 or later of
Tcl. It has also been tested on Windows 2000 and Tcl 8.4 but any
bugs specific to these platforms will not be fixed.

INCOMPATIBILITY This version does not
support the twapi_desktop and twapi_server package subsets of TWAPI and does not
provide a Tclkit format distribution.

INCOMPATIBILITY The command set_user_priv_level and the -priv
option to the get_user_account_info, set_user_account_info and new_user commands have
been removed as their use was unsuitable for domain environments.
Use specific group membership instead to control privileges.